Myths of Digital Music Part 4
Myth 1
Licensed Audio CDs Sound Better Than Your Copies
If during the copy there were no read / write errors (fatal) and the optical drive of the device on which the copy will be played has no problem with its reading, then this statement is wrong and easily refutable.
Myth 2
Stereo encoding mode offers better quality than Joint Stereo
This misconception mainly refers to LAME MP3, as all modern encoders (AAC, Vorbis, Musepack) use only Joint Stereo mode (and this already says something)
For starters, it’s worth mentioning that the Joint Stereo mode is used successfully with lossless compression. Its essence lies in the fact that the signal before encoding is decomposed into the sum of the left and right channels (Mid) and their difference (Side), and then these signals are encoded separately. At the limit (for the same information on the right and left channels) you get twice the data savings. And since the information in the left and right channels is quite similar in most music, this method is very effective and allows you to significantly increase the compression ratio.
In loss, the principle is the same. But here, in constant bitrate mode, the quality of fragments with similar information on two channels will increase (at the limit, it will double), and for VBR mode, in such places, the bitrate will simply decrease ( don’t forget that the main task of VBR mode is to stably maintain the given encoding quality, using the lowest possible bit rate). Since the sum of the channels is given priority (in the bit allocation) during lossy encoding to avoid degradation of the stereo panorama, dynamic switching between Joint Stereo (Mid / Side) frame-based stereo modes and normal (Left / Right) is used. By the way, the reason for this deception was the imperfection of the switching algorithm in previous versions of LAME, as well as the presence of the Forced Joint mode, in which there is no automatic switching.
